1. Field of the Invention
The present invention relates to an electron beam sterilizer for caps, in which caps are irradiated by an electron beam and sterilized while they are conveyed.
2. Description of the Related Art
Conventionally, there is known an electron beam cap-sterilizer in which caps are irradiated by an electron beam and sterilized while the caps are continuously conveyed. In such an electron beam cap-sterilizer utilizing an electron beam, a cap chute, which is disposed inclined in a downward direction, is usually used as a conveying device for supplying the caps to an electron beam radiating device, as disclosed in Japanese Unexamined Patent Publication (Translation of PCT Application) No. 2011-520713. In the electron beam cap-sterilizer disclosed in this publication, caps are separated one by one using a star-wheel, and are sent out to the cap chute, in which each of the caps is rolled down and is irradiated by an electron beam.
On the other hand, in an electron beam cap-sterilizer disclosed in Japanese Unexamined Patent Publication No. 2010-285197, a cap makes contact with a surface of an inclined conveying passage while not in contact with another surface of the conveying passage, so that the cap is rotated due to the friction from contact. An electron beam radiating device is provided in a predetermined range contained in the conveying passage, to radiate an electron beam onto the rotating cap through a radiation window of the electron beam radiating device, by which the cap is sterilized. In the electron beam cap-sterilizer disclosed in this publication, a star-wheel is disposed at the lower end of the conveying passage in order to intermittently eject a cap from an outlet of the conveying passage.
In the electron beam cap-sterilizer disclosed in '713, the electron beam is emitted in a section in which caps moving through the cap chute are rotated. However, in the section in which the caps are freely rotated, the caps are accelerated due to the force of gravity. Therefore, a radiation distance through which the electron beam is emitted should be long enough to ensure a radiation time that is sufficient to sterilize the caps, and thus, the electron beam radiating device must be large in order to radiate a wide-ranging beam.
On the other hand, in the electron beam cap-sterilizer disclosed in '197, the star-wheel for ejecting caps is provided on the downstream side of the radiating section of an electron beam. In such a structure, caps come into contact with each other in the radiating section. Therefore, the caps rotate very little because of the friction, and thus, the surface of the cap is not uniformly irradiated by the electron beam.